Method and apparatus for plating metallic surfaces



Feb. l7, 1931. DUNKLEY 1,793,069

METHOD AND APPARATUS FOR PLATING METALLIC SURFACES Filed Jan. 23, 1928 Patented Feb. 17, 1931 UNITED" STATES PATENT OFFICE.

EDWARD O. DUNKLEY, OF RICHMOND, CALIFORNIA, ASSIGNOR TO STANDARD OIL COM- PANY OF CALIFORNIA, OF SAN FRANCISCO, CALIFORNIA, A CORPORATION OF DELA- WARE MDTEOD' AND APPARATUS FOR PLATING METALLIC SURFACES Application filed January 23, 1928. Serial No. 248,607.

This invention relates to a method of continuously plating extended metallic surfaces with another metal such as chromium by electrical deposition. The invention also relates to a method of continuously plating extended metallic surfaces by electrical deposition from an electrolytic solution, whereby an even coating is deposited and oxidation of the metallic surfaces prevented before such deposition.

One of the objects of this invention is to disclose a method for plating the interior surfaces of large metallic vessels used in oil refining processes with chromium.

Another object is to disclose a method whereby extended surfaces may be plated with ametal continuously.

Another object is to disclose a method whereby oxidation of the surfaces to be plated is prevented prior to plating with *a'metal.

Another object of this invention is to provide a means for electroplating extended surfaces of metal vessels and means to control temperature, quantity and quality of electrolyte.

Another object is to provide means whereby extending metallic surfaces .may be continuously plated and the occlusion of gases in the metallic covering substantially reduced.

Another object is to provide means whereby extended surfaces of metallic vessels may be continuously plated with a metal and concentration of the plating solution.

A still further object is to accomplish such plating with comparatively small electrode areas, power consumption and solution requirements, and to provide means of platmg the interior surfaces of large cylindrical vessels without creating laps in the finished plating. Other. objects andadvantages of this invention will become apparent from the following description of the method and apparatus. o

It is well known that hydrocarbon oils from many sources contain active constituents such as sulfur compounds and the like which are injurious to the interiors of vessels in which they are treated, due to corrosive means for regulating the temperatureand' action. This condition is particularly prevalent in cracking processes and wherever petroleum oils are treated at high temperatures or pressures, and this corrosion occurs by reason of the release of corrosive vapors durlng the process and their increased activity at the temperatures used.

particularly resistant to the action of these corrosive agents and that the interiors of containers, receptacles and the like employed in the various stages of petroleum refining or cracking may be protected against deterioration by plating with chromium by the electrolytic method. One method of lating such vessels is described in United tates Patent No. 1,582,407 issued to Kenneth V. King, in which a water-tight cell is pressed against the surface to be plated and held in position while an electrolytic solution is circulated through the cell and the electric current is passed between the anode, comprising the side of the cell not in contact with the surface being plated, and the cathode, which in this case is that portion of the surface in contact with the solution.

The objections to this method are the labor required to set up the cell after each area is plated, the waste due to lapping of successive or adjacent areas amounting to as much as 40% of the entire surface covered, and the necessity for freshly cleaning the surface immediately before deposition of metal thereon due to rapid'oxidation of such surfaces.

Another method by which the interiors of such large vessels such as stills, evaporators and other containers, may be plated is by filling the entire vessel with solution and using a series of slowly revolving staggered vanes for anodes so that the individual anode area is comparatively small, and at the same time the entire inner surfacecan be plated It is also known that metallic chromium is in a single'operation. Disadvantages of. this area,'which in this case is a variable portion of the shell of the vessel, to be much larger than the corresponding anode area. While deposition of metal does not occur over this entire area of cathode, there is still a considerable passage of current through the solution which is doing no useful work and causing decomposition of the solution itself.

This invention is directed to disclose an apparatus and method of plating extended metallic surfaces such as the interiors of large vessels in which the objections to both of the before-mentioned processes are overcome. In accordance with this invention, the deposi-. tion of metal is done continuously, uniformly, without laps and subsequent irregularity of the plated surface and with a single setup of the apparatus. The anode and cathode areas are such as to efficiently function under the available current and there is no necessity for maintaining any great excess of solution over that required for the actual work. Furthermore, all. oxidation of the clean surface prior to the application of the plating metal'is avoided by the manner in which the work is performed. Means have been provided whereby the concentration, temperature and effectiveness of the plating solution may be maintained or controlled so as to produce a uniform plating or coating.

These results are accomplished by means of a movable anode and cell so arranged that it is capable of plating a complete zone of the interior surface of the vessel and in its movement plating successive zones continuously until the entire interior surface is uniformly covered. Oxidation prior to plating is prevented by keeping the clean surface constantly bathed and covered with solution whereby the metal surface is rendered passive against rusting.

For purposes of illustration of the apparatus embodying this invention, reference will be made to the attached drawings, in which v Figure 1 represents rather diagrammatically a sectional view of a cylindrical vessel being plated by the apparatus and method which are the subject of the invention. Figure 2 shows a modified form of shell, while Figure 3 is a horizontal section along the line 83 through the cell shown in Figure 2.

Referring to the drawings, 1 is the shell of a cylindrical vessel such as a pressure still evaporator containing the traveling cell 2 which is suspended within the shell by means of an insulated wire orrope 3 which enables the cell to be drawn up within the shell at a proper predetermined speed by means of a drum and suitable hoisting apparatus, which is not shown. The cell 2 is kept concentrically within the shell by means of rollers 4 which are capable of limited movement in a direc" tion substantially perpendicular to the plane of the shell by means of plungers and springs or other activating means within the cylin ders 5. These rollers 4 are mounted upon the cell 2 at suitable distances around its periphery and their position in relation to thecentral vertical axis of the shell and cell may be adjusted in addition to the limited motion imparted to said rollers 4. by the activating means within the cylinders 5. The cell 2 forms a chamber 6 between the shell 1 and the anode or plurality of anodes 7, said anodes being insulated suitably from the rest of the cell and connected by suitable flexible electrical supply means 8 passing through an insulating sleeve 29 with a source of electrical energy (not shown). Any suitable portion of the shell 1 is connected as indicated at 9 with the negative terminal of a source of electrical supply so as to enable the shell to function as the cathode during the subsequent electrolytic deposition of metal.

Electrolytic solution is supplied to the interior of the shell through an annular header 10 positioned in the upper end of the shell and having a slot or slots 11 so positioned as to direct a flow of electrolyte or plating solution against the interior surface of the shell. This solution runs down into the cell 2 and is retained within the chamber 6 by means of a rubber or other suitable ring 12 attached to the under side of the cell 2 and yieldingly engaged with the interior surface of the shell 1. Positive contact between the ring 12 and the interior surface of the shell may be made by means of: suitable springs 13 having one end thereof attached to the cell 2 and the other end pressing against the movable edge of the rubber ring or a bearing strip 14 attached to such movable edge. After the chamber 6 is filled with the electrolytic solution, it may be discharged from said chamber by means of outlets 15 which direct the overflow from the chamber 6 into the space below the cell. Such electrolyte may then be discharged through the outlet 16 and led by any suitable means, such as the pipe means 17,

into a storage or control tank 18. The tank 18 may be equipped with heating or cooling coils 19, a valved inlet 20 and a valved outlet 21, said outlet from tank 18 being connected with a pump or other suitable device22 which is capable of supplying the header 10 with solution through the pipe means 23. Thermometers or other temperature indicating or recording instruments such as 24 and 25 may be positioned in the inlet and outlet lines to tank 18 or one of said thermometers or a third one may be positioned so as to indicate the temperature within tank 18.

It will be noted that air or other gas may be admitted to the interior of shell 1 through opening 26 and forcibly withdrawn through the vent opening 27 by means of a blower or fan 28 whereby a circulation of air may be maintained within the shell and the fumes of solution at too high a rate. The cell 2 may be made. from any desirable number of sections such as are-shown in Figure 3 so as to facilitate the assembling of the entire cell 2 within the shell 1, each section being of sufiiciently small size to permit it to be readily 1lgserted into the shell through the out In the operation of my method with the assistance of the abo vedescribed apparatus for plating the interior of a large cylindrical vessel with a metal, for example chromium, the shell 1 is preferably placed in a vertical position and connected with the negative terminal of a source of electrical supply.

The entire interior surface of the shell 1 is then thoroughly cleaned by mechanical and chemical means to provide a suitable surface for receiving the metal to be deposited. Cell 2 is next assembled within the shell at the lowest point. thereof and the actuating cable 3 and the positive electrical conductors 8 are attached-as 7 indicated.

. The solution circulating pump 22 is then i i started and the electrolyte, with which tank 18 has been filled and which has been-brought up to the proper temperature, is then forced through pipe means 23 to the distributing header 1.0 in the top of the shell. Through the slot in the annular header 10, the electrolyte is-discharged in a flat stream against the interior of the shell and fiowsdownwardly thereon entering the annular chamber 6 and keeping the intermediate surface bathed with solution, thereby protecting'the clean metal against oxidation. When the annular chamber 6 is completely filled with solution, the

excess is discharged through the overflow pipe 15 out through the outlet 16 and is carried back through pipe means 17 into the storage tank 18, thus maintaining the solution in the annular chamber 6 at a constant level.

Electric current under conditions of proper current density and voltage is then turned on and the fan orblower 28 started so as to create a suction within the shell to prevent the accumulation of dangerous fumes or gases. During plating with high current densities, largeivolumes of gas. such as hydrogen, are evolved and often occluded by the plating metal. By plating in the partial vacuum created by the fan 28 within the shell, such occlusion may be materially reduced and the deposition of metalin an impervious substantially indestructible coating facilitated. As the deposition of metal from the solution in the annular chamber 6 on the shell surface proceeds, the cell 2 is raised by means of the cable 3 at a rate consistent with the results desired until the entire inner surface is covered with a, uniform coating of metal. During the operation, the temperature of the outgoing solution may be closely observed by means of the thermometer 24 inthe discharge line, and a proper working temperature is maintained in the storage tank 13 by means of the heating or cooling coils 19 and thermometer 25. The concentration or quality of the electrolyte may be maintained by taking samples from the tank 18 and adding suitable acids or salts to the. solution through the inlet 20. If desirable, the solution discharged from the shell 1 through outlet 17 may be filtered or otherwise treated before being recirculated through the shell.

' While the entire shell 1 serves as the negative conductor, it is apparent that only the part-directly facing the anode 7 and bounded by the solution in the annular chamber 6 acts as the'cathode. The distance separating the anode from the cathode may be varied to anode and cathode are not to be regarded as fixed by the depth of solution or the separation of electrodes as described for it is evident that either electrode may be partially shielded by the intei position of plates of non conductive material. The anode-cathode area ratio has been found to be a major factor in plating with chromic acid baths, particularly in the case of excessively large-vessels. Thus the anode area should be as large as possible to avoid undue formation of reduced chromium oxides or chromium chromate which seriously interfere with the proper plating even though the greatly increased resistance of the electrolyte, due-to their presence is overcome.

Any suitable electrolytic solution containing chromic acid maybe employed for the deposition of chromium and as this invention does not pertain to the use of any particular solution or electrolyte, the composition of these plating solutions will not be given here.

While the invention has been particularly described as an apparatus and method for the electroplating of large cylindrical vessels with chromium, it is not limited to the deposition of chromium, nor to the deposition of chromium upon petroleum refining equipment. It is apparent that other metals 7 may be deposited out of the electrolytic solu-.

tions in the same manner and other types of surfaces or other equipmdnt may be so plated.

For example, cookers and digesters used in various industries, such as, for example, the wood pulp industry, may be very advantageously plated with the resistant metals such as chromium, vanadium, cobalt or combinations of these metals together or with chromium. Furthermore, the polarity of the electric current may be reversed and by employing a suitable electrolyte the invention may be used for the electrolytic cleaning of surfaces prior to plating or any other instances where such cleaning is desirable. The invention may also be used for the plain acid pickling of surfaces without the aid of electric current if the apparatus is constructed of acid resisting materials.

Various modifications and changes may be made in the construction or assemblage of the apparatus, and the invention is not to be limited to the particular construction shown in the drawings but is of .the scope of the appended claims.

I claim:

1. An apparatus for continuously treating interior surfaces of metallic vessels comprising a continuous ring-like electrolyte chamber bearing an electrode and forming with the adjacent surface of said metallic vessel an electrolytic cell, means for moving said chamber in a plane parallel to said surface, means for supplying electrolyte to said cell, and means for maintaining a substantially constant volume of electrolyte in said cell.

2. An apparatus for continuously electrodepositing metals upon interior surfaces of cylindricalvessels comprising a continuous ring-like electrolyte chamber bearing an electrode and forming with a portion of said interior surfaces an electrolytic cell, means for moving said chamber in a plane parallel to the interior surface of said vessels, means for circulating electrolyte through said cell, and means for supplying electrical energy to said electrode during the movement of said chamber within said vessels.

3. An apparatus for continuously plating interior surfaces of cylindrical metallic vessels with a metal comprising, a sectional cell bearing an electrode, said sectional cell being adapted to be assembled within the vessel to be plated and conform to the interior surface thereof, means for retaining electrolyte between said electrode and the surface to be plated, means for supplying to and maintaining an electrolyte in said cell, means for moving said cell and electrode in a plane parallel to the surface to be plated, and means for supplying electrical energy to said electrode during its motion. a

4. An apparatus for continuously plating interior surfaces of cylindrical oil refining vessels with a metal comprising, a sectional electrolytic cell hearing an anode and adapted to be assembled within said vessel to form a continuous circular cell, means for adjustably positioning said cell with respect to the interior surface of said vessels, means for maintaining the lower portion of the cell in adjustable and sliding contact with the interior surface of said vessels, and means for moving the cell in a plane parallel to the surface to be plated.

5. An apparatus for electro-deposition of chromium upon interior surfaces of cylindrical metallic oil refining vessels comprising, a sectional electrolytic cell bearing an anode and adapted to be assembled within said vessels, means for suspending and moving such cell within said vessels in a plane parallel to the interior surface thereof, means for covering the surfaces to be plated with a film of electrolyte, means for supplying electrolyte to said cell, means for retaining and maintaining a substantially constant volume of electrolyte in said cell between the anode and the surface to be plated, and means for supplying electrical energy to said anode.

6. An apparatus for continuously plating interior surfaces of cylindrical metallic oil refinin g vessels with chromium comprising, a sectional electrolytic cell and anode adapted to be assembled within said vessels, means for suspending and moving the cell and anode within said vessel in a plane parallel to the interior surface thereof, means for circulating electrolyte over the surfaces to be plated and through the cell, means for supplying electrical energy to said anode, means for regulating the temperature and quality of electrolyte during circulation thereof, and means for removing gases from said vessels.

7. A method of continuously treating extended metallic surfaces comprising covering the surfaces to be treated with a film of electrolyte, and moving an electrolyte chamber bearing an electrode and adapted to form an electrolytic cell with the surface to be treated in a plane substantially parallel to the surface to be treated, the rate at which the chamber is moved and the distance between the electrode carried thereby and the surface to be treated depending upon the treatment desired.

8. A method of continuously treating interior surfaces of cylindrical vessels comprising, positioning an electrolyte chamber hearing an electrode and adapted to form an electrolytic cell with the interior surface to be treated within said vessels, covering the surfaces to be treated with a film of electrolyte, circulating electrolyte through said chamber, and moving the chamber in a plane parallel to said interior surfaces.

9. A method of continuously plating interior surfaces of cylindrical vessels comprising, positioning an electrolyte chamber bearin g an electrode and adapted to form an electrolytic cell with the interior surface to be treated within said vessels, circuating an electrolyte over the surfaces to be treated and through the chamber, moving the chamber and electrode in a plane parallel to said interior surfaces, and supplying electrical energy to the electrode during this motion.

10. A method for continuously plating interior surfaces of cylindrical vessels comprising, cleaning said surfaces, positioning an electrolytic cell within said vessels, circulating an electrolyte over the interior surfaces of said vessels and through said cell, supplying electrical energy to an electrode within said cell, and moving said cell in a plane parallel to the interior surfaces to be plated.

11. A method of continuously plating interior surfaces of cylindrical vessels in successive zones comprising positioning an electrolyte chamber bearing an anode within said vessel, said electrolyte chamber being adapted to form an electrolytic cell with a portion of the interior surface of said vessel, circulating an electrolyte over said surfaces to be plated and through said chamber, maintaining a substantially constant volume of electrolyte between the anode and the surface to be plated Within said chamber, moving the anode and chamber in a plane substantially parallel to the surface to be plated, and supplying electrical energy to the anode, a portion of the surface to be e plated acting as the cathode. I

12. A method of continuously plating interior surfaces of cylindrical oil refining vessels with chromium comprising, positioning a movable electrolytic cell and anode within said vessel, circulating a film of electrolyte over the surfaces to be plated and through said cell, maintaining a substantially constant volume of electrolytewithin the cell, removing excess electrolyte from said cell to prevent accumulation of objectionable substances therein, removing fumes from said vessels, moving the cell and anode in a plane parallel to the surface being plated, and supplying electrical energy to said cell and anode, a portion of the vessel being plated acting as a cathode.

Signed at Richmond this 13th day of December, 1927.

EDWARD O. DUNKLEY. 

